The image diagnosis techniques (optical imaging techniques) have been widely utilized in various sites such as device machine, semiconductor, medical treatment, and so on. For example, the X ray CT, the nuclear magnetic resonance, the ultrasonic observation, and the like are exemplified that are able to take the tomographic image in addition to the general microscopy in the manufacturing site for precision machine, semiconductor, and the like and the medical site.
In recent years, the OCT (Optical Coherent Tomography) technique that utilizes optical coherence has been paid attention as an approach of the image diagnosis. The near infrared ray with the wavelength of 1300 nm is often used for the light source, and the near infrared ray is noninvasive to the organism and is superior in the spatial resolution because of its shorter wavelength than the ultrasonic wave, which allows for the identification of approximately 10 to 20 μm and therefore, in particular, the further use in the medical site is expected. The exemplary structure of the OCT endoscope is as disclosed in Patent document 1, for example.
By the way, in the OCT endoscope disclosed in Patent document 1, the rotational force of a motor is transferred to a rotation shaft via a belt and further transferred to a lens unit via a flexible shaft extending through in an optical sheath. Therefore, ablation powder is likely to occur due to the friction between the inner circumference surface of the optical sheath and the flexible shaft, and rotation unevenness, rotation transfer delay, torque loss, and the like are likely to occur due to the friction, deflection, and/or torsion of the flexible shaft, elastic deformation of the belt, and so on.
Further, as a technique for overcoming the above-described problems, in the invention of Patent document 2, a motor is arranged so as to face the front end of an optical fiber and a reflection mirror is provided at the front end surface of the rotation shaft of the motor. In this invention, however, the body of the motor is located more front than the reflection mirror, which may cause the problems that the power supply cable for the motor may be bent toward the optical fiber side, that the power supply cable may be located in the side of the reflection mirror and block the light reflected by the reflection mirror and thus a part of the whole 360-degree circumference may be a shade resulting in the limitation of the angle of view, and that a protruding part that is more front than the reflection mirror (a part incorporating the motor body) may come into contact with the object resulting in the limitation of the imaging range in the probe axis direction. Further, when the motor is rotated continuously at a high speed, the deviation of the film pressure of the lubricating oil at the bearing part is likely to cause rotation unevenness, axis vibration, and the like called as jitter (the phenomenon in which the rotation angle fluctuates), face tangle error (the phenomenon in which the rotation end surface tilts), and whirl (the phenomenon in which the rotation axis vibrates).
Furthermore, the axis displacement and the like due to them may cause the light transmission loss to be increased.